Post-World War II baby boomers are reaching age 65 and over (older adults), and are projected to drive more miles later in life compared to previous generations. This demographic shift raises national-level traffic safety concerns, because older adult drivers have an elevated crash rate, are more likely to be injured in a crash, and are less likely to recover from injuries and resume the level of daily life activity prior to bing injured. States have enacted various licensing laws pertaining to older drivers. To date, little research has investigated the effectiveness of these laws in protecting not only older drivers, but also those who share the roadways with them. It remains unclear how these laws affect driving behaviors among older adults, whether they reduce driver injuries per driving hours or trips, the extent to which they increase the use of alternative transportation, and whether there are corresponding increases in injuries to older adults as passengers or pedestrians. Therefore, we propose a four-year project with objectives to determine, across multiple states, the impact of licensing laws for older adults on driving decisions, alternative transportation choices, and rates of injurious and fatal crashes among older adult drivers, passengers, pedestrians, and bicyclists. We hypothesize that the effectiveness of licensing laws is impacted by certain provisions of the law, and that the licensing laws reduce driving trips and injuries, but increase non-driving trips and injuries. The aims of this project are to determine which provisions of licensing laws reduce driving hours and trips, licensure rates, and crash rate per driving hours (Aim 1), to identify which provisions of laws increase alternative transportation and non-driving injury and fatality (Aim 2), and to identify which provisions of laws affect total transportation trips, hours, and crashes among older adults (Aim 3). The following legislative provisions will be examined: means of renewal (in-person or mail/online), length of the renewal cycle, requirements for vision tests, requirements for road tests, requirements for knowledge tests, and mandatory physician reporting for medical conditions. The aims will be accomplished by combining and analyzing travel, license, economic, legislative, population, and crash data from a variety of data systems maintained by federal, state, and private agencies. Multilevel generalized linear and negative binomial models will be used to estimate the effects of state-level laws on individual-level travel behaviors and state-level crash rates. Guided by strong preliminary data, this study is also innovative. For example, the innovative measurement of crash rate per hour of driving in combination with crash rate per capita will help determine whether the effects of the legislative provisions in reducing crash rate per capita are due to a reduction in driving hours, due to safer driving, or due to some combination of both. This study is significant, because the findings can inform policymakers' efforts to update or modify existing legislation to effectively reduce injurios crashes among older adults while preserving their personal freedom and mobility.